A2 rated extension & upgrade, Co Cork
This upgrade and extension to a rural home in County Cork cut its energy use by almost 90%, bringing it to the cusp of an A1 Building Energy Rating.
Two engineers brought their technical minds to this retrofit and extension in Carrigtwohill, Co Cork — and created a warm, energy efficient home in the process. Emma and Rob had each owned separate homes, but after getting married decided to put one up for sale. “His house was on a site in the country where both of us preferred to live,” Emma says — so they decided to sell her house. Parts of Rob’s 1980s cavity wall house were cold and damp, other parts were fine. But the layout wasn’t ideal, and the couple wanted to make the space more efficient and usable. Being engineers, they were keen to get their teeth stuck into the technical details. “We weren’t going to compromise on the energy side of it,” says Emma. The couple interviewed various architects and selected Cork-based Andrew Lane. Their main design goals were to maximise natural light and views over the east Cork countryside, and to create a modern, open plan living space in the extension — thus allowing them to re-task rooms in the old house. But the project stalled when it took Emma a year to sell her old house. This turned out to be a blessing in disguise, as it gave the couple
more time to research low energy building. Carrigaline-based Vinro Ltd was appointed builder, while John Roche – then of Permagreen – was insulation and airtightness contractor for the retrofit of the old house. Not wanting to lose any floor space, Emma and Rob chose to insulate the original house externally with 150mm of graphite EPS, finished with mineral render and installed by John Roche, who also pump-filled the existing 50mm cavity with Isothane Technitherm polyurethane foam. The attic had previously been insulated with 300mm of mineral wool between the joists. But as part of the upgrade John Roche sprayed the sloping rafters with an extra 150mm of Isothane Duratherm, a rigid polyurethane spray-foam. Getting the insulation and airtightness right in the old part of the house was the biggest challenge, says architect Andrew Lane. “We in effect wrapped the building to create a warm structure, but the existing floor structure was a challenge as we did not want to take up the existing floor slab,” he says. The solution here was to lay 50mm of Kingspan PIR insulation on top of the existing slab. The extension was constructed with a factory-
built timber frame from Cygnum. Emma and Rob opted for the company’s Precision 300 wall system, which delivers a wall spec pitched at the passive house market, including a U-value of 0.13. The couple always preferred timber frame over block. “It’s warmer, it goes up a lot quicker than block. We didn’t want a long construction schedule,” Emma says. Cygnum’s Heber McMahon calls Precision 300 the “Rolls Royce” of their timber frame systems. This was one of the first projects in which it was used, but he says demand has grown rapidly since. The walls are insulated with 300mm of factoryfitted cellulose, with an insulated thermal break in the studwork to prevent cold bridging. The service cavity is packed with high density Metac mineral wool. Emma was attracted to the efficiency of a closed panel system — one that arrives pre-insulated, rather than being pump-filled on site. The sloping extension roof features 300mm of high-density Metac mineral wool between the rafters, while a flat-roofed section has 400mm of the same. Airtightness is provided by German-manufactured Gerband tapes and membranes, supplied by Clean Energy Ireland.